This invention relates to a new and improved barrier design for separating resistors in a thermal ink jet printer.
The prior art with regard to thermal ink jet printing is adequately represented by the following U.S. Pat. Nos.: 4,243,994; 4,296,421; 4,251,824; 4,313,124; 4,325,735; 4,330,787; 4,334,234; 4,335,389; 4,336,548; 4,338,611; 4,339,762; 4,345,262; 4,345,263; and 4,353,079. The basic concept there disclosed is a device having an ink-containing capillary with an orifice for ejecting ink, and an ink heating mechanism, generally a resistor, in close proximity to the orifice. In operation, the ink heating mechanism is quickly heated, transferring a significant amount of energy to the ink, thereby vaporizing a small portion of the ink and producing a bubble in the capillary. This in turn creates a pressure wave which propels an ink droplet or droplets from the orifice onto a nearby writing surface. By controlling the energy transfer to the ink, the bubble quickly collapses before it can escape from the orifice.
In these systems, bubble collapse can cause cavitation damage to the resistor and premature failure of the device. It is known in the art that barriers placed between adjacent resistors to inhibit cross-talk lengthen device lifetime, and that enclosing each resistor on three-sides further increases lifetime. However, with three-sided barriers, ejected ink droplets do not travel perpendicular to the plane of the resistor structure, and cavitation damage to the resistor still remains a primary mode of failure.